Gas cylinder



FIG. 1 is a front view of a gas cylinder in accordance with the design;

FIG. 2 is a left side view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a front and left side perspective view thereof;

FIG. 6 is a front and left side perspective view thereof in an open configuration;

FIG. 7 is a front and right side perspective view thereof; and,

FIG. 8 is an enlarged top view thereof.

The broken lines in the drawing views are included for the purpose of illustrating portions of the gas cylinder that form no part of the claimed design. 

The ornamental design for a gas cylinder, as shown and described. 